580-5M-15 Belt Some Chuweng Raser or xcooter thunder THS Big Wheel scooters used this belt from factory with 20 tooth trans sprocket to later find it became too long over time...unless your scooter has a 24 tooth trans sprocket. Reccomend superceding to 585-5m-15 belt if you are using a 24 tooth engine/trans 5m belt sprocket. The most common belt used for the left side or clutch belt with a 20 tooth engine sprocket and a 60 tooth shaft sprocket is a 575-5m-15. replacement of dry rotted twisted mis-shapen motor mounts can cause belt tension & alignment issues and incorrect length choice or misdiagnosis. your motor can be adjusted forward and backwards slightly to help with belt tension. we recommend replacing the motor mounts if the motor mounts are dry rotted or they stay twisted with the transmission belt removed.